Mareks Doniks, of Edgbaston Road, was approached by an Environment Agency enforcement officer while returning to his vehicle after being seen fishing at the Ripple Fishery, in Gloucestershire.
He was asked to produce his rod licence but was unable to do so. The officer told Doniks he had been seen fishing on the river earlier in the day.
After speaking with Doniks, officers returned to the location where he had been seen fishing.
They discovered a bag containing a dead bream and eel.
At a court appearance, Doniks pleaded not guilty claiming he was sitting on the riverbank but not fishing.
But Stroud Magistrates Court found him guilty of one charge relating to fishing without a rod licence.
He was ordered to pay a £50 fine, £717 costs and £15 victim surcharge - a total of a £782.
The offence took place on August 9 last year.
The court was told Environment Agency enforcement officers were patrolling as part of Operation Stone, a programme of targeted fisheries operations to reduce illegal fishing, fish removal and theft on the rivers Severn and Avon.
Speaking after the hearing, a spokesman for the Environment Agency said they were pleased with the sentence given to Doniks.
And they said it would be a stark warning to others who attempted to so the same thing.
The spokesman said: "No matter where anglers choose to fish in England they need a rod licence.
"The money raised by the sale of the licences helps us to carry out vital work to help maintain, develop and protect fisheries.
"This case sends out a clear message that we will not hesitate to prosecute individuals when they do not abide by the law."